Bilateral phonon transport modulation of Bi-layer TMDCs (MX2, M=Mo, W; X=S)

Abstract

The weakly van der Waals interactions make monolayer TMDCs straightforward to vertically stack to bilayer systems, which have attracted enormous attention because of their potential applications in optoelectronics and electronic devices. In particular, MoS2/WS2 heterostructure exhibits excellent performance in photodetectors. The thermal transport behavior plays a vital role in life and performance of devices, which have been rarely reported. Here, the thermal properties and thermal transport mechanism of monolayer MoS2 and WS2, bilayer MoS2 and WS2 and MoS2/WS2 heterostructure are systematically investigated by first-principles calculations and Boltzmann transport theory. The results indicate that the thermal conductivity of bilayer systems is considerably higher than that of correlated monolayer systems. Most interesting, the thermal conductivity of MoS2/WS2 heterostructure is not only much lower than the thermal conductivity of 2L-WS2 and 2L-MoS2, but also much lower than that of monolayer WS2 and MoS2. The harmonic properties mainly including phonon dispersion and anharmonic properties mainly including scattering rate and Grüneisen parameters are used to elucidate the corresponding mechanism. Moreover, the underlying electronic properties mainly including interlayer charge transfer and interlayer coupling play an essential role in thermal transport of MoS2/WS2 heterostructure. The results suggest that the thermal conductivity of TMDCs can be largely tunes by various combinations, such as WS2/WS2 or WS2/MoS2, which provides an effective way for manipulating the thermal transport properties of MoS2 and WS2 for future emerging applications.